/Engine/Plugins/Online/OnlineServices/Source/OnlineServicesCommon/Public/Online/SessionsCommon.h
[TOnlineResult](API\Plugins\OnlineServicesInterface\Online\TOnlineResult)< [FAddSessionMember](API\Plugins\OnlineServicesInterface\Online\FAddSessionMember) > AddSessionMemberInternal ( const [FAddSessionMember::Params](API\Plugins\OnlineServicesInterface\Online\FAddSessionMember\Params) & Params )